Just in case it helps:
CCC doesn't handle the EFI. You have to handle that.
A CCC clone is a Mac-specific volume level copy, not a partition or block level copy. In this sense it's not a drive clone, but a system specific copy. This is akin to Windows data migration tools like get bundled with new drives and are aware of Windows specific layout details. CCC is very Mac aware, but not EFI.
By default, a clone is a Data partition only, no system.
The bootable backup assistant can copy the whole drive but requires erasing the target volume, which must be APFS to start. I believe any existing EFI contents are not touched—but I might be wrong.
In a thread from a year ago it was learned that a bootable (APFS Replicator) clone must be made while booted from the drive to be copied, or the target may not be bootable. That news was reported to come directly from Bombich. I should assume that CCC would now warn you about this... Idk There may have been a misunderstanding about the distinction between an APFS Replicator clone (Apple SW guided by CCC) and a CCC Data partition clone,